When a machine tool effects a tapping with utilization of synchronization of a axial feeding and a rotation of a spindle of the machine tool, the rotation of the spindle and a feeding movement amount of the axis of the spindle are controlled to be synchronized with a pitch of the tapping. In an actual machining; however, due to e.g. a phenomenon called “servo delay”, an error sometimes occurs in the pitch of the tapping with failure of synchronism between tap rotation and axial feeding. Conventionally, this was prevented by providing floats on axially opposed sides of the tap holder. In recent years, thanks to improvement in (synchronizing) precision in the synchronization between the rotation and axial feeding, attributable to development in the mechanism and/or control technique, there is provided a float-less integral configuration.
Notwithstanding, despite the improvement in the synchronizing precision of the machine tool, when the axial feeding direction and the rotational direction are changed for e.g. detaching the tap from an object to be machined, there can occur mismatch of rotation of the spindle relative to the feeding of the spindle, which makes it impossible to eliminate completely occurrence of a minor movement of the tap in the axial direction, which in turn would result in inadvertent enlargement of the tapping hole or deterioration in the machining performance.
As an arrangement for absorbing the above-described synchronization error, there has been proposed an arrangement in which a chuck (a tap collet) is clamped along the axial direction to a bottom face of an attachment recess of a holder body and a fastener nut via an elastic member. With provision of such elastic member, there will occur a small movement in the axial direction between the holder body and the chuck, which movement can absorb synchronization error between the axial feeding and rotation of the spindle of the machine tool.